#include <stdio.h>
#include <string.h>

int main(int argc, const char *argv[])
{
	int flag=0;
	int arr[8]={1,3,5,7,9,11,13,15};
	int a=0;
	int b=7;
	int mynum;
	int mid=(b+a+1)/2;
	printf(">>>plz input your num\n");
	printf(">>> ");
	scanf("%d",&mynum);
	while(mynum!=arr[mid])
	{
		if(mynum>arr[mid]&&mynum<arr[b])
		{
			a=mid;
			mid=(b+a+1)/2;
		}
		else if(mynum<arr[mid]&&mynum>arr[a])
		{
			b=mid;
			mid=(b+a+1)/2;
		}
		else if(mynum==arr[a]||mynum==arr[b])
		{
			break;
		}
		else
		{
			flag=1;
			break;
		}
		if(a+1==b&&mynum!=arr[a]&&mynum!=arr[b])
		{
			flag=1;
			break;
		}
	}
	if(flag==1)
	{
		printf("NULL\n");
	}
	else
	{
		printf("good\n");
	}
	
	return 0;
}
